• noun Brit. informal a person’s head.
— ORIGIN originally denoting a large marble: of unknown origin.
The word bonce is slang for head, mainly used in London. It appears to have derived from the game 'Bonce' - a children's game played with large glass marbles.
I can remember my Dad, a Cockney by the truest definition, calling my sister and I bacon bonce when, as children, we did something particularly stupid. I have grown up believing that a bacon bonce is therefore a stupid person. Not so! Bacon Bonce is Cockney Rhyming Slang for nonce meaning 'child molester'!
I'll have to put Dad right ...
I've got a pain in me bonce
Shut up! You're doing me bonce in